DE102018129969A1 - Sensor membrane, membrane cap and optochemical sensor - Google Patents

Abstract

The invention relates to a sensor membrane (3) for an optochemical sensor (1, 10) for determining a measurement variable that correlates with a concentration of an analyte in a measurement fluid, comprising: - a functional layer (23) which has a first polymer matrix which contains a luminescent dye (24) is doped, the emissivity of which can be changed by the analyte after excitation with electromagnetic radiation; and a second polymer matrix in which the functional layer (23) is at least partially encapsulated and which is permeable to the analyte at least in a partial area facing the measuring fluid and adjacent to the functional layer (23); characterized in that the sensor membrane (3) comprises an optically detectable substance (27) different from the luminescent dye (24) for identifying the sensor membrane (3). The invention further relates to a membrane cap with such a sensor membrane and an optochemical sensor.

Description

The invention relates to an optochemical sensor for determining a measurement variable correlating with a concentration of an analyte in a measurement fluid.

Optochemical sensors for measuring the concentration or the partial pressure of certain substances, so-called analytes, in measurement media are based on the principle of the analysis-induced quenching of the luminescence (luminescence quenching) of a luminescent, e.g. fluorescent or phosphorescent substance, hereinafter also referred to as luminescent dye. This substance can be an organic dye, for example. Examples of luminescence are fluorescence and phosphorescence.

Often, optochemical sensors have a membrane containing the luminescent dye, which is often formed from one or more polymer materials. For the measurement, the membrane is brought into contact with the measuring medium so that the analyte can penetrate the membrane and interact with the luminescent dye. Such membranes can comprise a layer system, with individual layers of the layer system each having a special chemical composition, different from the other layers, and correspondingly special properties. Layers can thus be provided which bring about a selectivity of the sensor by selectively permitting diffusion of the analyte to deeper layers of the layer package. Other layers can contain the luminescent dye. Additional layers can bring about a mechanical or chemical stabilization of the layer package or can be designed to absorb ambient light that would interfere with the measurement. Such layers, the properties of which influence the function of the sensor, are also referred to as functional layers of the membrane. For stabilization, membranes of optochemical sensors can comprise a substrate on which further layers of the membrane are applied and bound by physical or chemical methods.

Over their operating time, such sensor membranes are subject to aging, which leads to a gradual deterioration in the sensor properties, e.g. a sensor drift. For example, substances present in the functional layers can degrade and / or be discharged or washed out of the membrane in contact with the measuring medium. This applies in particular to the luminescent dye. A reduction in the concentration of the luminescent dye in the sensor membrane can lead to a reduction in the sensitivity of the optochemical sensor and, if appropriate, also to measurement results which are highly erroneous. The inevitable aging of the sensor membranes, even under moderate operating conditions, is caused by extreme operating conditions, e.g. through sterilization processes or contact with aggressive media such as strong acids or alkalis. Under such conditions, within a short time, i.e. Even after just a few measurements, the sensor membrane is damaged to such an extent that the sensor no longer appears suitable for further use. Such damage can consist, for example, of detaching individual layers of the sensor membrane.

Out DE 10 2014 112 972 A1 an optochemical sensor is known which maintains its functionality even under harsh environmental conditions, for example with regular sterilization of the sensor membrane or regular cleaning processes with hot lye. This sensor comprises a sensor membrane which has a sensor element with at least one functional layer in which a luminescent dye is contained. The sensor membrane further comprises a matrix in which the sensor element is fully embedded. The matrix consists of a material which is permeable to the analyte at least in a partial area facing the medium and adjacent to the sensor element. Embedding the sensor element in a matrix ensures that the functional layers of the sensor element at least do not come into direct contact with aggressive media and additionally protects the functional layers against mechanical detachment. This reduces the risk of damage and delays the aging of the sensor membrane due to the discharge of substances from the functional layers.

Despite these measures to protect against aging and damage, sensor membranes are often wearing parts that have to be replaced regularly. For example, there are optochemical sensors that have a sensor body and a membrane cap that can be detachably connected to the sensor body. While the sensor body contains long-lasting optical and electrical or electronic components of the sensor, which are used for luminescence excitation, the acquisition of measurement signals and the processing of the measurement signals, the membrane cap comprises the sensor membrane, which has a much shorter life. The membrane cap can be exchanged for a new membrane cap with a new, similar sensor membrane if the sensor membrane is damaged or can no longer be used due to signs of aging.

Sensor membranes and / or membrane caps are therefore often self-contained, ie without an associated sensor body, as accessories optochemical sensors for sale. In order to ensure the optimal functioning of an optochemical sensor with such a replaceable membrane cap or a replaceable sensor membrane, care should be taken to ensure that it is only suitable and / or for the respective application in which the sensor with the new membrane is to be used Sensor bodies matched sensor membranes can be combined with the sensor body to form an optochemical sensor.

If, on the other hand, the sensor body and the sensor membrane are equipped and specified for different applications (and therefore not coordinated with one another), the functionality of the sensor, both in terms of measuring the analyte concentration and in terms of possible diagnostic functions, may be impaired. This applies even more if the sensor membrane is of poor quality or has been tampered with (product piracy). Confusion of sensor membranes or the use of sensor membranes that may not be of a quality intended for the sensor body should therefore be avoided as far as possible. A label provided on the packaging of the sensor membrane does not appear to be sufficiently secure against accidental confusion or manipulation.

The object of the invention is to provide a stable and long-lasting sensor membrane for an optochemical sensor and an optochemical sensor with such a sensor membrane, which comprises a secure identifier for identifying the sensor membrane, the identifier ideally not or only with very great effort can be manipulated or faked.

This object is achieved by a sensor membrane according to claim 1, a membrane cap according to claim 15 and an optochemical sensor according to claim 17. The invention also comprises a method for testing and / or identifying a sensor membrane of an optochemical sensor according to claim 18. Advantageous embodiments are shown in FIGS dependent claims specified.

• - eine Funktionsschicht, welche eine erste Polymermatrix aufweist, die mit einem Lumineszenzfarbstoff dotiert ist, dessen Emissionsvermögen nach einer Anregung mit elektromagnetischer Strahlung durch den Analyten veränderbar ist; und
• - eine zweite Polymermatrix, in der die Funktionsschicht zumindest teilweise eingekapselt ist, und die zumindest in einem dem Messfluid zugewandten und an die Funktionsschicht angrenzenden Teilbereich für den Analyten durchlässig ist;

wobei die Sensormembran eine von dem Lumineszenzfarbstoff verschiedene, optisch detektierbare Substanz zur Kennzeichnung der Sensormembran umfasst.The sensor membrane according to the invention for an optochemical sensor for determining a measurement variable correlating with a concentration of an analyte in a measurement fluid comprises:

• a functional layer which has a first polymer matrix which is doped with a luminescent dye, the emissivity of which can be changed by the analyte after excitation with electromagnetic radiation; and
• a second polymer matrix in which the functional layer is at least partially encapsulated and which is permeable to the analyte at least in a partial region facing the measuring fluid and adjacent to the functional layer;

wherein the sensor membrane comprises an optically detectable substance different from the luminescent dye for identifying the sensor membrane.

By using an optically detectable substance contained in the sensor membrane to identify the sensor membrane, the sensor membrane can be identified by a simple optical test method. In this way it can be checked whether a sensor membrane is suitable for use with a specific sensor body or for use in a specific application. In a special application, the label can also offer protection against product piracy.

The functional layer can be formed as a layer having one or more island-shaped functional layer elements.

The second polymer matrix can be formed from the same polymer material as the first polymer matrix. The difference between the first polymer matrix and the second polymer matrix is then that the first polymer matrix is doped with the luminescent dye.

The sensor membrane can have a layer package with a front outer surface intended for contact with the measurement fluid and a rear outer surface which is connected to a substrate.

The second polymer matrix can encapsulate the functional layer in such a way that a first layer of the second polymer matrix covers the functional layer and a second layer of the second polymer matrix is arranged between the functional layer and the substrate, the first and second layers of the second polymer matrix being in one Functional area surrounding area are chemically and / or physically connected. The second polymer matrix at least partially encapsulates the functional layer. In an advantageous embodiment, the second polymer matrix completely encapsulates the functional layer.

In advantageous configurations, the first and / or the second layer of the second polymer matrix can be doped with the optically detectable substance for identifying the sensor membrane.

In addition to the doping with the luminescent dye, the first polymer matrix of the functional layer can be doped with the optically detectable substance for identifying the sensor membrane.

The optically detectable substance can be selected from the group consisting of: organometallic compounds such as metal porphyrin complexes, polyazaannulene dyes, in particular polyaza [18] annulene dyes, azaborone dipyrromethenes (AzaBODIPY), boron dipyrromethenes (BODIPY) and metal phthalocyanine complexes.

The optically detectable substance can differ from the luminescent dye, for example, in that it comprises another central ion and / or one or more other ligands. If the optically detectable substance is a dye that can be stimulated to luminescence, the dye is advantageously selected so that its luminescence is not from the same substance, i.e. the same analyte, e.g. extinguished or intensified, like the luminescence of the luminescent dye. In order not to impair the function of an optochemical sensor using the sensor membrane, the emission spectra of the luminescent dye used to determine the analyte concentration and the optically detectable substance should be clear, i.e. measurable, differentiate. Such a difference can consist, for example, in that the optically detectable substance can be excited for luminescence with radiation of a first wavelength, and the luminescent dye can be excited for luminescence with radiation of a second wavelength, which differs measurably from the first wavelength, the optically detectable substance radiation of the second wavelength cannot be excited to luminescence. Another possibility is that the radiation emitted by the optically detectable substance after excitation has a different wavelength or a different wavelength range than the luminescent radiation emitted by the luminescent dye after excitation.

The optically detectable substance can be a high conversion material (photon upconversion material), in particular in the form of nanoparticles (UCNPs = upconversion nanoparticles).

The optically detectable substance can comprise one or more inorganic luminescent pigments which consist of an inorganic solid which itself shows donor-acceptor luminescence or charge transfer luminescence or is doped with one or more luminescent ions, the one or more luminescent ions is or are selected from the group consisting of: In ⁺ , Sn ²⁺ , Pb ²⁺ , Sb ³⁺ , Bi ³⁺ , Ce ³⁺ , Ce ⁴⁺ , Pr ³⁺ , Nd ³⁺ , Sm ²⁺ , Sm ³⁺ , Eu ²⁺ , Eu ³⁺ , Gd ³⁺ , Tb ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ²⁺ , Tm ³⁺ , Yb ²⁺ , Yb ³⁺ , Ti ³⁺ , V ²⁺ , V ³⁺ , V ⁴⁺ , Mn ²⁺ , Mn ³⁺ , Mn ⁴⁺ , Fe ³⁺ , Fe ⁴⁺ , Fe ⁵⁺ , Co ³⁺ , Co ⁴⁺ , Ni ²⁺ , Cu ⁺ , Ru ²⁺ , Ru ³⁺ , Pd ²⁺ , Ag ⁺ , Ir ³⁺ , Pt ²⁺ and Au ⁺ .

The optically detectable substance can comprise an electrochromic material.

The functional layer can be covered with a protective, supporting and / or insulating layer which is permeable to the analyte. Such a layer can, for example, be applied directly to the functional layer. Alternatively, it is also possible for the protective, support and / or insulating layer to be embedded in the second polymer matrix surrounding the functional layer, for example in the form of a support grid embedded in the polymer matrix. For example, the protective, supporting and / or insulating layer can be at least partially embedded in the second polymer matrix covering the functional layer. The protective, support and / or insulating layer can consist of several individual layers.

The protective, support and / or insulating layer can be formed from a polymer doped with a pigment, in particular a dark pigment such as carbon black or activated carbon. This pigment is used to absorb radiation that is interfering with the measurement and / or to protect the luminescent dye.

A membrane cap of an optochemical sensor can comprise a sensor membrane according to one of the configurations described above and a, in particular cylindrical, housing, the sensor membrane being arranged on an end face of the housing.

On its side opposite the end face, the housing can be designed to be detachably connected to a sensor body. The sensor body can be optical components, e.g. comprise a radiation source and a detector for luminescent radiation emitted by the luminescent dye of the sensor membrane and a sensor circuit for controlling the radiation source and for processing signals from the detector. The sensor circuit can also be designed to use the detector signals to generate, possibly process, and output measurement signals for determining a concentration of an analyte.

• - ein Sondengehäuse, welches mindestens einen zum Eintauchen in das Messfluid gestalteten Eintauchbereich aufweist, wobei die Sensormembran, vorzugsweise mittels einer Membrankappe in dem Eintauchbereich des Sondengehäuses angeordnet ist;
• - eine in dem Sondengehäuse angeordnete Strahlungsquelle zum Einstrahlen von Anregungsstrahlung in die Sensormembran;
• - einen in dem Sondengehäuse angeordneten Strahlungsempfänger zum Empfangen von Strahlung, die durch den Lumineszenzfarbstoff und/oder die optisch detektierbare Substanz emittiert wird; und
• - eine in dem Sondengehäuse angeordnete Sensorschaltung, welche dazu ausgestaltet ist, die Strahlungsquelle zu steuern, Signale des Strahlungsempfängers zu empfangen und auf den Signalen des Strahlungsempfängers basierende Ausgabesignale zu erzeugen und auszugeben.

The invention also comprises an optochemical sensor for determining a measurement variable correlating with a concentration of an analyte in a measurement fluid with a sensor membrane according to one of the configurations described above, further comprising:

• a probe housing which has at least one immersion area designed for immersion in the measuring fluid, the sensor membrane, preferably by means of a Membrane cap is arranged in the immersion area of the probe housing;
• a radiation source arranged in the probe housing for irradiating excitation radiation into the sensor membrane;
• a radiation receiver arranged in the probe housing for receiving radiation which is emitted by the luminescent dye and / or the optically detectable substance; and
• a sensor circuit arranged in the probe housing, which is designed to control the radiation source, to receive signals from the radiation receiver and to generate and output output signals based on the signals of the radiation receiver.

As described above, the probe housing can be configured in several parts. For example, it can comprise a first part that forms a sensor body, in which the sensor circuit, the radiation source and the radiation receiver are accommodated, and a second part that can be detachably connected to the first part and that includes the sensor membrane. The second part can be designed, for example, in the form of a cap. The two parts of the probe housing can be releasably connected to one another again by means of a plug, clamp or screw connection.

For the measurement, at least one immersion area of the probe housing encompassing the sensor membrane in the measuring fluid, e.g. a measuring liquid, immersed.

The sensor can be set up for measuring different analytes in that it has a memory in which parameters serving to determine different measured variables, for example concentrations of different analytes, are stored. For example, for the measurement of the concentration of a first analyte (e.g. oxygen), a first parameter set comprising, for example, a wavelength and / or modulation frequency of the radiation source, calibration parameters or a sensitivity of the radiation receiver, and for the measurement of the concentration of a second analyte (e.g. pH -Value, CO ₂ , Na ⁺ , K ⁺ ) a second parameter set, including, for example, a wavelength and / or modulation frequency of the radiation source, calibration parameters or a sensitivity of the radiation receiver. It is thus possible to convert the sensor by exchanging a first membrane, which contains a luminescent dye for the detection of the first analyte, for a second membrane, which contains a luminescent dye for the detection of the second analyte, in each case for the measurement by means of the sensor circuit the parameter set suitable for the sensor membrane is selected. Such a membrane exchange can be used to convert an oxygen sensor to a pH sensor, for example. The membrane exchange is advantageously brought about by exchanging a first membrane cap for a second membrane cap, it being possible for the membrane caps to be designed as described above.

In this case, the optically detectable substance contained in the sensor membrane can advantageously be used to identify the type of analyte that can be determined by means of the sensor membrane. This can be done automatically by the sensor itself, as will be explained further below. On the basis of the recognized sensor membrane or the identified type of analyte, the sensor can select the parameters stored in the memory for the analytes to be determined with the sensor membrane and use them for determining the measured values.

• - Prüfen mittels eines optischen Detektionsverfahrens, ob die Sensormembran eine von dem Lumineszenzfarbstoff verschiedene optisch detektierbare Substanz enthält.

The invention also relates to a method for testing and / or identifying a sensor membrane of an optochemical sensor with a functional layer which has a first polymer matrix which is doped with a luminescent dye, the emissivity of which can be changed by an analyte after excitation with electromagnetic radiation, and which has a second polymer matrix in which the functional layer is at least partially encapsulated and which is permeable to the analyte at least in a partial region facing the measuring fluid and adjacent to the functional layer, comprising:

• - Check by means of an optical detection method whether the sensor membrane contains an optically detectable substance that is different from the luminescent dye.

• - Anregen der optisch detektierbaren Substanz zur Emission von elektromagnetischer Strahlung;
• - Erfassen eines Signals eines Strahlungsempfängers, der dazu eingerichtet ist, Emissionsstrahlung der in der Sensormembran enthaltenen optisch detektierbaren Substanz zu empfangen und in ein elektrisches Signal zu wandeln; und
• - Ermitteln anhand des erfassten Signals, ob die Sensormembran die optisch detektierbare Substanz enthält.

The verification step can include the following steps:

• - stimulating the optically detectable substance to emit electromagnetic radiation;
• - Detection of a signal of a radiation receiver which is set up to receive emission radiation from the optically detectable substance contained in the sensor membrane and to convert it into an electrical signal; and
• - Determine on the basis of the detected signal whether the sensor membrane contains the optically detectable substance.

As mentioned, the optically detectable substance itself can be analytically sensitive, but it is advantageously not analytically sensitive, ie that when the optically detectable substance from this emitted radiation is not influenced by the analyte with regard to its wavelength, its intensity or the course of its intensity as a function of time. In this case, it is ideally not influenced by other possible constituents of the measuring liquid.

The optically detectable substance can be excited by irradiating excitation radiation of one or more specific wavelengths into the sensor membrane. Irradiation of excitation radiation can be carried out using a radiation source of the sensor or a radiation source that is independent of the sensor, for example a radiation source of a test device. Accordingly, the detection of the signal of the radiation receiver by means of a radiation receiver of the sensor or by means of a radiation receiver independent of the sensor, e.g. that of a separate test device. The determination of whether the sensor membrane contains the optically detectable substance can be carried out by means of a sensor circuit of the sensor or by means of a circuit of a test device which is independent of the sensor and which is connected or can be connected to the radiation receiver. For this purpose, a user or the sensor circuit or the circuit of the test device can automatically automate a characteristic of the radiation received by the radiation receiver with a target characteristic, for example stored in a memory of the sensor or the test device, e.g. one or more reference values. The characteristic can be, for example, a wavelength, an intensity, an intensity profile, a spectrum or a phase angle.

• - Prüfen mittels eines weiteren, insbesondere optischen oder chemischen, Verfahrens, ob die Sensormembran die optisch detektierbare Substanz enthält.

In addition, a further test step can be carried out, which includes:

• - Check by means of a further, in particular optical or chemical, method whether the sensor membrane contains the optically detectable substance.

If the step of checking reveals that the sensor membrane contains an optically detectable substance, the method can further comprise identifying the optically detectable substance. The identification can take place, for example, on the basis of the radiation receiver signal detected in the optical detection method or a value derived therefrom with a catalog of reference values, each reference value representing a specific optically detectable substance. Such reference values can e.g. Intensities, phase angles, or wavelengths of absorption or luminescence maxima. The reference values can be stored in a memory of the sensor or the test device.

Checking by means of an optical detection method whether the sensor membrane contains an optically detectable substance and, if the check shows that the sensor membrane contains an optically detectable substance, identifying the optically detectable substance from the optochemical sensor can be done by means of a radiation source and a radiation receiver of the optochemical Sensor and a sensor circuit and / or a higher-level electronics connected to the sensor circuit can be performed.

As described, the optically detectable substance contained in the sensor membrane forms a captive, non-manipulable identification of the sensor membrane. This can not only serve to identify the sensor membrane as suitable for a certain application or to counter product piracy. Additionally or alternatively, a traceability of the sensor membrane can also be ensured by means of an optically detectable substance introduced into the sensor membrane. This can be used by the manufacturer of the sensor membranes. For example, over a certain first period, e.g. over a year or over a month, a first optically detectable substance can be added to sensor membranes. After the end of the first period, a second, optically detectable substance different from the first can be added to the sensor membranes produced in a subsequent second period. The first and second optically detectable substance can be selected such that they emit radiation of different wavelengths when excited or are excited to emit radiation by excitation radiation of different wavelengths. In this way, sensor membranes produced in the first and the second period can be distinguished.

Analogously, different optically detectable substances can also be used for different production batches of sensor membranes. In the event of quality errors in individual batches, this enables all copies of the affected batches to be found.

Furthermore, the labeling of sensor membranes by means of the optically detectable substance can be used to label sensor membranes which are used for determining a concentration of a specific analyte. For example, a sensor membrane that has a first luminescent dye that is used to detect a first analyte can be labeled with a first optically detectable substance, while a sensor membrane that has a second luminescent dye that is used to detect a second analyte can be labeled with one other, second optically detectable substance can be characterized.

By changing the sensor membrane, this allows a sensor to be converted completely automatically (in the sense of a “plug & play” functionality) from a sensor for determining the concentration of the first analyte to a sensor for determining the concentration of the second analyte. As described above, such a sensor can be set up for measuring different analytes by having a memory in which the determination of different measured variables, e.g. Concentrations of different analytes, serving parameters are stored. The sensor can automatically determine which of these parameters the sensor is using in a current measurement by performing, in a first step, preferably by means of its radiation source and its radiation receiver, the test as to whether the sensor membrane currently used in the sensor is an optically detectable substance different from the luminescent dye contains. In the event that the test reveals that such an optically detectable substance is present in the sensor membrane, the sensor can identify the optically detectable substance in a second step. For this purpose, for example, the signal of the radiation receiver or a value derived from the signal can be compared in the optical test with reference values each representative of different optically detectable substances. Each reference value corresponds at the same time to a specific analyte that can be determined using the sensor membrane. Based on a match of the optical signal with one of the reference values, the optically detectable substance or the corresponding analyte can be identified as the substance represented by the reference value or as the corresponding analyte. Based on the identification of the substance, the sensor can thus select and apply the parameters to be used for measurements below.

This method is particularly advantageous and simple to use if the sensor membrane is changed by changing the membrane cap, as described above.

The check as to whether an optically detectable substance is contained in the sensor membrane and the identification of the optically detectable substance can be carried out by the sensor circuit alone or by a higher-level unit, e.g. wired or wirelessly connected to the sensor circuit for communication, e.g. a transmitter or an operator panel.

• 1 einen optochemischen Sensor nach einem ersten Ausführungsbeispiel;
• 2 einen optochemischen Sensor nach einem zweiten Ausführungsbeispiel;
• 3 ein erstes Ausführungsbeispiel einer Sensormembran für einen optochemischen Sensor;
• 4 ein zweites Ausführungsbeispiel einer Sensormembran für einen optochemischen Sensor;
• 5 ein drittes Ausführungsbeispiel einer Sensormembran für einen optochemischen Sensor; und
• 6 ein viertes Ausführungsbeispiel einer Sensormembran für einen optochemischen Sensor.

The invention is explained in more detail below on the basis of the exemplary embodiments illustrated in the figures. Show it:

• 1 an optochemical sensor according to a first embodiment;
• 2nd an optochemical sensor according to a second embodiment;
• 3rd a first embodiment of a sensor membrane for an optochemical sensor;
• 4th a second embodiment of a sensor membrane for an optochemical sensor;
• 5 a third embodiment of a sensor membrane for an optochemical sensor; and
• 6 a fourth embodiment of a sensor membrane for an optochemical sensor.

In 1 is schematically in a longitudinal sectional view of an optochemical sensor 1 shown according to a first embodiment. The sensor 1 is designed in the present exemplary embodiment for determining a concentration of a gas, for example dissolved oxygen, dissolved in a measuring liquid. The sensor 1 has a probe housing 2nd on, which is configured essentially cylindrical in the embodiment shown here. The probe housing 2nd is at its front end, intended for contact with a measuring medium, through a sensor membrane 3rd locked. The sensor membrane 3rd comprises, inter alia, a luminescent dye embedded in a polymer matrix, the luminescence of which is quenched by the analyte, here, for example, oxygen. Alternatively, the luminescent dye can also have the property that its luminescence is enhanced by the analyte. This is the case, for example, for optical pH detection with luminophores based on the PET effect (PET = photo-induced electron transfer). The sensor membrane 3rd can have a stabilizing substrate and a plurality of layers applied to the substrate. Their detailed structure is shown below using the 3rd to 6 are explained in more detail.

In the probe housing 2nd is a source of radiation 4th arranged, which may include one or more LEDs, for example. In the probe housing 2nd is also a radiation receiver 5 arranged, which can include, for example, one or more photodiodes. The probe housing 2nd also contains an optical fiber 6 from the radiation source 4th emitted radiation to the sensor membrane 3rd leads and from that in the sensor membrane 3rd embedded luminescent dye emitted luminescent radiation to the radiation receiver 5 directs. The light guide 6 can be one or more include optical fibers. In the exemplary embodiment shown here, the light guide 6 formed by a bundle of fibers that has a first arm 6.1 which has the radiation source 4th with the sensor membrane 3rd connects, and that a second arm 6.2 having the radiation receiver 5 with the sensor membrane 3rd connects. The radiation source 4th and the radiation receiver 5 are electrical with a sensor circuit 7 connected. The sensor circuit 7 is designed to be the radiation source 4th to stimulate and control the emission of radiation. Next is the sensor circuit 7 designed to receive signals from the radiation receiver 5 that are from the radiation receiver 5 represent, receive and process received luminescent radiation. The processed signals serve as measurement signals from the sensor 1 and can from the sensor circuit 7 via an interface 8th to a higher-level unit, for example a transmitter, a controller, a computer or an operating device. the interface 8th can be a fix with the sensor circuit 7 connected cable connection, a detachable plug connection with galvanic contacts or a galvanically isolated, in particular inductively coupling, plug connection. About that with the interface 8th connected cables 9 can the sensor circuit 7 with energy, also to operate the radiation source 4th , are supplied. Furthermore, the sensor circuit 7 Signals, especially data, over the cable 9 transmitted to the higher-level unit and, optionally, signals, in particular data, received by the higher-level unit.

The acquisition of measured values and the evaluation of the signals of the radiation receiver 5 to determine a measured value can be between the sensor circuit 7 and the parent unit. For example, the sensor circuit 7 even to control the radiation source 4th be designed. For this purpose, it can comprise a microcontroller which is in a memory of the sensor circuit 7 stored computer program that executes the control of the radiation source 4th serves to record measured values. Alternatively, at least some of the functions of the control can also be carried out by the higher-level unit, which then generates corresponding control signals for actuating the radiation source 4th to the sensor circuit 7 sends. Correspondingly, the microcontroller can process the radiation from the radiation receiver 5 detected signals in a memory of the sensor circuit 7 Execute the stored computer program that is used to evaluate the signals to determine measured values. The correspondingly processed signals can be measured signals representing the measured values via the interface 8th be output to the higher-level unit.

In contact with the measuring liquid, which contains the analyte in a certain concentration, the analyte penetrates into the polymer matrix and interacts with the luminescent dye. The luminescent dye is emitted by radiation from the radiation source 4th stimulated to emit luminescent radiation, the luminescence is quenched depending on the concentration of the analyte, for example during oxygen detection in the polymer matrix. However, it is also possible to increase the fluorescence or phosphorescence in the opposite case (for example in the case of an optical pH measurement). The sensor circuit 7 detected by means of the radiation receiver 5 characteristic parameters, such as the luminescence intensity, the phase shift of the luminescence signal or also the decay time of the luminescence and determines a measured value of the analyte concentration present in the measuring medium by comparison with a calibration function.

In operation of the sensor 1 can the sensor membrane 3rd are subject to aging, in particular if they are subjected to regular sterilization or cleaning processes over their operating life, in which they are exposed to high temperatures and possibly also aggressive cleaning media, for example hot sodium hydroxide solution. This can even damage the sensor membrane 3rd come that another use of the sensor 1 no longer makes sense. In this case, the sensor membrane 3rd against a new sensor membrane 3rd be replaced. For this, the sensor 1 if necessary, be put out of operation for a longer period of time, as the sensor membrane has to be replaced 3rd the probe housing 2nd must be opened.

In 2nd is a schematic longitudinal sectional view of a second embodiment of an optochemical sensor 10th shown. The sensor 10th of the second embodiment is essentially identical to the sensor 1 of the first embodiment ( 1 ), however, is an exchange of the sensor membrane 3rd with this sensor 10th less expensive. Identically designed components of the sensors 1 , 10th according to the first embodiment ( 1 ) and according to the second embodiment ( 2nd ) are identified with identical reference symbols.

The sensor 10th has a sensor membrane 3rd with a luminescent dye, a radiation source 4th , a radiation receiver 5 and an optical fiber designed as a fiber bundle 6 on the the radiation source 4th and the radiation receiver 5 with the sensor membrane 3rd connects so that excitation light of the radiation source 4th on the sensor membrane 3rd hits and in the sensor membrane 3rd luminescent radiation emitted by the luminescent dye to the radiation receiver 5 reached. It also includes one with the radiation source 4th and the radiation receiver 5 electrically connected sensor circuit 7 that have an interface 8th can be connected to a higher-level unit. A power supply for the sensor circuit 7 and a transfer of data from the sensor circuit 7 to the higher-level unit via a cable 9 . The sensor circuit 7 can be configured analogously to the sensor circuit 7 of the sensor 1 according to the first embodiment and provide identical functions.

The in 2nd shown sensor 10th differs from the sensor 1 of the first embodiment essentially by the construction of its probe housing 11 , which is built here in two parts. It comprises a first cylindrical housing part, which has a sensor body 12 forms. This sensor body 12 includes the components of the sensor 10th that have a long lifespan, such as the sensor circuit 7 and the optical components, ie the radiation source 4th and the radiation receiver 5 as well as the light guide 6 . At its front end, the sensor body can 12 be open or have a window that is transparent to the excitation radiation and the luminescence radiation.

The probe housing 11 includes a second housing part that has a membrane cap 13 forms. This can be detached with the sensor body 12 get connected. In the present exemplary embodiment, the connection is by a screw connection 14 realized. The membrane cap 13 has a cylindrical housing, the sensor membrane at its front end 3rd having. The membrane cap has a thread on the back 15 on that with a complementary thread 16 of the sensor body 12 to form the screw connection 14 cooperates.

This structure allows easy replacement of the sensor membrane 3rd by the membrane cap 13 thanks to a new, identical membrane cap 13 can be replaced. In this way, the replacement of the sensor membrane requires 3rd no longer decommissioning the sensor 10th .

Based on 3rd to 6 the structure of the sensor membrane is now becoming closer 3rd described. In 3rd is a first possible configuration of the sensor membrane 3rd shown in a schematic longitudinal sectional view. The sensor membrane 3rd comprises a substrate 20th , as well as one on the substrate 20th arranged stack of layers of functional and encapsulation layers. The substrate 20th can consist of a material which is transparent to the excitation and luminescence radiation, for example made of glass, ceramic, a polymer, an organometallic compound or zeolite. The substrate material may also have a hybrid structure and be composed of at least two materials selected from the aforementioned materials. This includes, for example, the use of a hybrid material made from two or more polymers or from two or more different ceramics or glasses.

The sensor membrane 3rd further comprises a first functional layer 23 from one or more island-shaped layer elements (in the 3rd to 6 only such an island-shaped layer element is shown). The first functional layer 23 consists of a first polymer matrix, in which a luminescent dye 24th is embedded. The luminescent dye 24th serves as a specific indicator for one using the optochemical sensor 1 or 10th analytes to be detected. The first polymer matrix can be formed from a polymer or a polymer blend which on the one hand is permeable to the analyte and on the other hand with the luminescent dye 24th is doped. For example, silicone, porous or non-porous PVDF, PVF, Teflon AF, Hyflon AD, Nafion, a copolymer or terpolymer or n-polymer with a polystyrene unit, for example polystyrene-co-vinylpyridine, polystyrene-co-vinylpyridine-co-divinylbenzene, or a blend of several of the polymers mentioned.

The first functional layer 23 is encapsulated in a second polymer matrix. In the present exemplary embodiment, this is achieved in that between the substrate 20th and the functional layer 23 sandwich a first layer 21st the second polymer matrix is arranged, and that the first functional layer 23 completely from a second layer 22 of the second polymer matrix is covered in such a way that around the island-shaped layer element of the first functional layer 23 around the first layer 21st and the second layer 22 the second polymer matrix lie directly on top of one another and are physically and / or chemically connected to one another. The second polymer matrix is the first functional layer in at least one 23 covering sub-area of the second layer 22 permeable to the analyte. Preferably, a polymer or a polymer blend is selected as the material of the second polymer matrix, which is chemically stable with respect to the measuring medium and with respect to commonly used cleaning media, such as sodium hydroxide solution. Ideally, to make the optochemical sensor as universal as possible 1 , 10th to allow, the material of the second polymer matrix is also suitable for applications in the field of food technology. The second polymer matrix can advantageously consist of the same material as the first polymer matrix, but the second polymer matrix is not coated with the luminescent dye 24th endowed. By encapsulating the first functional layer 23 or the luminescent dye contained therein 24th will the lifespan of the Sensor membrane 3rd lengthened because the encapsulation has a protective function for the first functional layer 23 Has. For example, the diffusion or washing out of the luminescent dye 24th from the first functional layer 23 delayed out from the start. Even if luminescent dye 24th from the first functional layer 23 Diffusing into the second polymer matrix, the chemical environment of the luminescent dye essentially does not change, so that the sensor membrane 3rd , at least for a while, their functionality does not lose, in the sense that the evaluation of the sensor membrane 3rd measurement signals obtained based on the calibration function leads to measurement values which still have a sufficient measurement quality. So that is in 3rd shown sensor membrane 3rd Can be used over longer periods of time than conventional sensor membranes, even under harsh conditions.

In the present embodiment, the second layer 22 the second polymer matrix a second functional layer 25th embedded, which can for example be a protective, support or insulation layer. For example, a layer made of a material that absorbs ambient light, for example a polymer layer containing carbon black, can be used as a protective layer. A mechanical support grid, for example made of a metal, can be used as the support layer. Of course, further functional layers can also be provided, which can be embedded in the second polymer matrix or arranged above or below the second polymer matrix.

In the present exemplary embodiment, the sensor membrane 3rd a final top layer 26 on. This can be formed from the same polymer material as the second polymer matrix. Alternatively, it can also be formed from another polymer material. The top layer 26 is optionally present, ie a sensor membrane according to the invention can also be designed such that the second polymer matrix is intended to be brought into direct contact with the measuring medium. The top layer 26 can consist of a material approved for the specific application (e.g. in the food or pharmaceutical sector). The material of the top layer 26 can also be optimized with regard to its resistance to chemically aggressive media or other harsh environmental conditions, eg high temperatures or high mechanical loads. The top layer 26 is at least partially permeable to the analyte.

In the in 3rd shown design of the sensor membrane 3rd is in an edge area of the top layer 26 that is not immediately above the functional layer 23 is arranged, an optically detectable substance 27th contain.

The optically detectable substance 27th can be a stable organic or inorganic substance or a hybrid material made of organic and / or inorganic substances or a mixture of organic and / or inorganic substances. Suitable materials are, for example, organometallic compounds, metal complexes such as metal porphyrin complexes, polyazaannulene dyes, metal phthalocyanine complexes, azaborone dipyrromethenes (AzaBODIPY), boron dipyrromethenes (BODIPY) or mixtures of these compounds. The optically detectable substance 27th is from the luminescent dye 24th different, for example in that if it is a metal complex in both cases, it has a different central ion and / or different ligands.

If it is the optically detectable substance 27th is a luminescent substance, its luminescence is ideally not achieved by means of the sensor membrane 3rd determinable analytes influenced, for example deleted or increased, by interference of the optically detectable substance 27th that act as a marking of the sensor membrane 3rd serves with the acquisition of measured values by means of the sensor membrane 3rd to avoid. However, this is not absolutely necessary, since it is also possible for the analyte to interact with the optically detectable substance 27th when calibrating the sensor 1 , 10th to be taken into account and appropriate compensation to be carried out when evaluating the measurement signals. The emission spectra of the optically detectable substance advantageously have 27th and the luminescent dye 24th measurable differences. For example, both substances can be luminescent dyes, the one in the first functional layer 23 luminescent dye contained 24th For example, luminescent radiation of a first wavelength is emitted while the optically detectable substance 27th Luminescence radiation of a second wavelength different from the first wavelength is emitted. There should be a distance of at least 20 nm, preferably at least 50 nm, between the first and the second wavelength.

The optically detectable substance 27th can also have a high conversion material (technical term: photon upconversion material). These materials convert low-energy into higher-energy photons in an anti-Stokes scattering process. These can be, for example, organic materials such as polycyclic aromatic hydrocarbons or inorganic materials such as ions of the d- or f-block elements. The optically detectable substance can be advantageous 27th consist of upconverting nanoparticles, e.g. quantum dots or lanthanoid-doped nanoparticles such as fluorides or oxides, e.g. NaYF ₄ , NaGdF ₄ , LiYF ₄ , YF ₃ , Gd ₂ O ₃ , doped with Er ³⁺ , Yb ³⁺ , Tm ³⁺ or more of these lanthanides.

The optically detectable substance 27th can be a stable inorganic material in further exemplary embodiments, for example an inorganic luminescent pigment from the series of solid phase substances which show donor-acceptor luminescence or charge transfer luminescence. For example, it can contain one or more ions from the following group: In ⁺ , Sn ²⁺ , Pb ²⁺ , Sb ³⁺ , Bi ³⁺ , Ce ³⁺ , Ce ⁴⁺ , Pr ³⁺ , Nd ³⁺ , Sm ^{2 +} , Sm ³⁺ , Eu ²⁺ , Eu ³⁺ , Gd ³⁺ , Tb ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ²⁺ , Tm ³⁺ , Yb ²⁺ , Yb ³⁺ , Ti ³⁺ , V ²⁺ , V ³⁺ , V ⁴⁺ , Cr ³⁺ , Mn ²⁺ , Mn ³⁺ , Mn ⁴⁺ , Fe ³⁺ , Fe ⁴⁺ , Fe ⁵⁺ , Co ³⁺ , Co ^{4 +} , Ni ²⁺ , Cu ⁺ , Ru ²⁺ , Ru ³⁺ , Pd ²⁺ , Ag ⁺ , Ir ³⁺ , Pt ²⁺ and Au ⁺ . It can also be a binary, ternary or quaternary halide, oxide, oxyhalide, sulfide, oxysulfide, sulfate, oxysulfate, selenide, nitride, oxynitride, nitrate, oxynitrate, phosphide, phosphate, carbonate, silicate, oxysilicate, vanadate, molybdate, germanate, tungstenate or include oxygermanate. These can include cations of the elements Li, Na, K, Rb, Mg, Ca, Sr, Sc, Y, La, Ti, Zr, Hf, Nb, Ta, Zn, Gd, Lu, AI, Ga and In.

The inorganic material can be used as a doping or in the top layer 26 embedded nanoparticles in the sensor membrane 3rd are available. The doping or the nanoparticles can form an image or a lettering, for example in the form of a lettering, a number or a logo, for example in the form of a hologram.

The optically detectable substance 27th can also be an electrochromic material in an alternative embodiment. Such materials change color with an electrical impulse, examples are indium tin oxide (ITO), Prussian blue or Berlin blue, lithium tungsten oxide and fluorine tin oxide. In this case, the sensor membrane 3rd Include electrodes or are in contact with electrodes via which to the sensor membrane 3rd or to an optically detectable substance 27th comprehensive layer of the sensor membrane, a voltage can be applied, which is dimensioned such that a color change of the optically detectable substance 27th occurs and can be optically detected.

It is also possible as an optically detectable substance 27th to use a substance that changes its color under the influence of a certain influencing variable, for example when there is a change in pressure or temperature or when irradiated with electromagnetic radiation.

For universal use of the sensor membrane 3rd To ensure, it is advantageous if all materials used can be sterilized up to a temperature of at least 140 ° C and / or autoclavable up to at least 121 ° C, and are stable against common cleaning agents and disinfectants, such as sodium hydroxide solution or ethylene dioxide. The materials used can advantageously also be selected such that they can also withstand sterilization with gamma radiation at a dose of at least 5 kGy without degenerating.

The optically detectable substance is also advantageous 27th stable up to a temperature of 140 ° C, as well as chemically stable against acids, bases and common disinfectants such as ethylene oxide. However, this is not absolutely necessary if the optically detectable substance is only used to label the sensor membrane 3rd to be used in the first installation of the sensor membrane 3rd to check their origin or their suitability for use with a specific sensor body or a specific application. A later destruction of the optically detectable substance 27th the use of the sensor then no longer plays a role, since detection of the substance 27th then is no longer required.

In 4th is an alternative embodiment of the sensor membrane 3rd shown. Identically designed parts of the sensor membranes according to the in 3rd illustrated embodiment and the in 4th Embodiment shown are shown with the same reference numerals. The sensor membrane 3rd has a substrate 20th on and a first functional layer 23 from a first polymer matrix with a luminescent dye immobilized therein 24th whose luminescence is quenched by the analyte, for example in oxygen detection, or increased, for example in optical pH detection with luminophores based on the PET effect (PET = photo-induced electron transfer). The first functional layer 23 is encapsulated in a second polymer matrix, in two layers 21st , 22 on the substrate and the first functional layer 23 is applied, completely analogous to the embodiment according to 3rd . In the second shift 22 the second polymer matrix is a second functional layer 25th embedded with soot pigments as a protective layer against ambient light. The sensor membrane 3rd is at its end intended for contact with the measuring medium through a cover layer 26 completed with an optically detectable substance across its entire cross-section 27th is endowed. The optically detectable substance 27th can one of the with reference to the embodiment of the 3rd substances mentioned. In contrast to using 3rd illustrated embodiment is in the in 4th sensor membrane shown 3rd however, pay attention to the optically detectable substance 27th to be selected so that it does not measure the luminescent radiation of the luminescent dye 24th interferes.

In 5 is another embodiment of the sensor membrane 3rd shown schematically. The Sensor membrane 3rd is identical to that in 3rd shown sensor membrane 3rd (The same reference numerals designate identical parts) with the only difference that the optically detectable substance 27th not in the top layer 26 but in the first shift 21st which is the first functional layer 23 with the luminescent dye 24th encapsulating second polymer matrix is included. This first layer 21st The second polymer matrix is in the present example with the optically detectable substance 27th endowed. The optically detectable substance 27th can be one of the aforementioned substances.

In 6 is a last embodiment of the sensor membrane 3rd shown schematically. It is also identical to that in 3rd shown sensor membrane 3rd (The same reference numerals designate identical parts) with the only difference that the optically detectable substance 27th not in the top layer, but in the first functional layer 23 together with the luminescent dye 24th is included. The optically detectable substance can also be used here 27th one of the previously in connection with the embodiment according to 3rd substances mentioned.

All of these configurations of the sensor membrane 3rd has in common that it is an optically detectable substance 27th contain that as captive with the sensor membrane 3rd associated labeling. This can serve to replace the sensor membrane 3rd to check whether the new sensor membrane to be used is suitable for use with the sensor 1 , 10th is. Additionally or alternatively, the marking can also serve as protection against counterfeiting (product piracy) or manipulation.

Furthermore, the marking can also be used to monitor a production process for sensor membranes or sensors, for example to avoid confusion of the sensor membranes during production, storage or distribution of the sensor membranes or of accessories comprising the sensor membranes, e.g. Membrane caps. The optically detectable substance can in particular serve to enable traceability of sensor membranes passed to users or accessories comprising the sensor membranes. In this way, costs that are caused by incorrectly assigned membranes or membranes incorrectly installed in the sensors can be avoided.

If different production batches of sensor membranes are provided with different optically detectable substances, a differentiation between these production batches is possible. For example, if an error occurs in only one production batch, all affected sensor membranes can be identified on the basis of the optically detectable substance that characterizes this production batch and can be removed from circulation.

The marking can also be used to automatically identify the analyte, which can be determined by means of the sensor membrane, and to automatically set sensor parameters used for the analyte determination.

For testing and / or identifying a sensor membrane 3rd can be carried out in the following way: On the one hand, an external, non-destructive detection of the in the sensor membrane can be done by means of an external device 3rd present optically detectable substance 27th be performed. On the other hand, the optochemical sensor in which the membrane is used can itself be used for optical detection in the sensor membrane 3rd present optically detectable substance 27th be performed. The radiation receiver can do this 5 and the sensor circuit 7 , and possibly the radiation source 4th be used. It is also possible for the sensor to comprise an additional radiation receiver and / or an additional radiation source, which is specific for the testing or identification of the sensor membrane 3rd , but not for the acquisition of measured values of the concentration of the analyte to be determined in the measuring operation of the sensor. In the 3rd to 6 arrows are drawn in, which symbolize the position of the test optics for the detection of the optically detectable substance: in the 3rd , 5 and 6 the test optics are arranged on the substrate side, so here the test can be carried out using the radiation receiver, for example 5 and / or the radiation source 4th of the sensor 1 , 10th take place or alternatively with a separate test device. In 4th If the inspection optics are arranged on the top layer side, the inspection is carried out using an additional inspection device.

There is also an optional alternative, the sensor membrane 3rd by means of a chemical or spectroscopic process, which usually destroys the sensor membrane 3rd to check. However, the test is preferably carried out non-destructively. For particularly difficult or critical cases, a destructive measurement can serve as additional proof, for example if a coherent batch from a large number of sensor membranes is being tested. In this case, one of the large number of membranes can be checked under destruction in order to additionally ensure the results of the non-destructive testing of the other membranes.

Suitable optical methods for non-destructive measurement with an additional device or with the means of the optochemical sensor itself are, for example, depending on the type of optically detectable substance used 27th , an optical luminescence measurement, an optical absorption measurement or an X-ray measurement. Atomic absorption spectroscopy or flame emission spectroscopy come into question as destructive, in particular wet chemical or spectroscopic, methods.

1. a) Emissionssignal oder -spektrum bei Anregung mit einer oder mehreren spezifischen Wellenlänge(n)
2. b) Absorptionssignal oder -spektrum gemessen in Reflexion
3. c) Polarisation von durch die optisch detektierbare Substanz emittierter oder von dieser gewandelter Strahlung, messbar mittels eines Polarisationsfilters
4. d) Optische Signale (z.B. Absorptionssignal gemessen in Reflexion) als Funktion der Temperatur, des Druckes, einer an die Sensormembran angelegten Spannung
5. e) Visuelle Detektion einer Verfärbung bei Änderung der Temperatur, des Drucks, bei Anlegen einer Spannung

All measuring methods known to the person skilled in the art can be used for optical luminescence or absorption measurements, for example detection of an intensity change, a phase angle, a decay time, an absorption or a reflection. The following measurements can be used in particular:

1. a) emission signal or spectrum when excited with one or more specific wavelength (s)
2. b) absorption signal or spectrum measured in reflection
3. c) Polarization of radiation emitted by or converted by the optically detectable substance, measurable by means of a polarization filter
4. d) Optical signals (eg absorption signal measured in reflection) as a function of the temperature, the pressure, a voltage applied to the sensor membrane
5. e) Visual detection of a discoloration when the temperature, the pressure changes, when a voltage is applied

Identification or testing can be carried out particularly reliably by using more than one measurement method. For example, two different non-destructive optical methods can be used to optically detect the optically detectable substance, e.g. one luminescence measurement and one absorption measurement in reflection, or two luminescence measurements in which different parameters are detected, e.g. a phase angle and a decay time.

In a further advantageous variant, the optically detectable substance 27th due to environmental conditions that lead to an above-average shortening of the life of the sensor membrane 3rd lead, such as higher temperatures than permitted by specification, or other improper handling of the sensor, irreversibly changeable. In this way, an examination of the optically detectable substance allows conclusions to be drawn about the remaining service life of the sensor membrane.

Reference symbol list

1

optochemical sensor

2nd

Probe housing

3rd

Sensor membrane

4th

Radiation source

5

Radiation receiver

6

Light guide

6.1

first arm

6.2

second arm

7

Sensor circuit

8th

interface

9

electric wire

10th

optochemical sensor

11

Probe housing

12

Sensor body

13

Membrane cap

14

Screw connection

15

thread

16

thread

20th

Substrate

21st

first layer

22

second layer

23

first functional layer

24th

Luminescent dye

25th

second functional layer

26

Top layer

27th

optically detectable substance

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102014112972 A1 [0005]

Claims (22)

Sensor membrane (3) for an optochemical sensor (1, 10) for determining a measurement variable correlating with a concentration of an analyte in a measuring fluid, comprising: - a functional layer (23) which has a first polymer matrix which doped with a luminescent dye (24) is whose emissivity can be changed by the analyte after excitation with electromagnetic radiation; and - a second polymer matrix in which the functional layer (23) is at least partially encapsulated and which is permeable to the analyte at least in a partial area facing the measuring fluid and adjacent to the functional layer (23); characterized in that the sensor membrane (3) comprises an optically detectable substance (27), different from the luminescent dye (24), for identifying the sensor membrane (3). Sensor membrane (3) after Claim 1 , wherein the functional layer (23) is formed as a layer having one or more island-shaped functional layer elements. Sensor membrane (3) after Claim 1 or 2nd , wherein the second polymer matrix is formed from the same polymer material as the first polymer matrix. Sensor membrane (3) according to one of the Claims 1 to 3rd The sensor membrane (3) has a layer package with a front outer surface intended for contact with the measurement fluid and a rear outer surface which is connected to a substrate (2). Sensor membrane (3) according to one of the Claims 1 to 4th , wherein the second polymer matrix encapsulates the functional layer (23) in such a way that a first layer (21) of the second polymer matrix covers the functional layer (23) and a second layer (22) of the second polymer matrix between the functional layer (23) and the substrate (20) is arranged, and wherein the first (21) and the second layer (22) of the second polymer matrix are chemically and / or physically connected to one another in a region surrounding the functional layer (23). Sensor membrane (3) after Claim 5 , wherein the first (21) and / or the second layer (22) of the second polymer matrix is / are doped with the optically detectable substance (27) for identifying the sensor membrane (3). Sensor membrane (3) according to one of the Claims 1 to 6 The first polymer matrix of the functional layer (23) is additionally doped with the optically detectable substance (27) for identification of the sensor membrane (3) in addition to the doping with the luminescent dye (24). Sensor membrane (3) according to one of the Claims 1 to 7 , wherein the optically detectable substance (27) is selected from the group consisting of: organometallic compounds such as metal porphyrin complexes, polyazaannulene dyes, in particular polyaza [18] annulene dyes, azaborone dipyrromethenes (AzaBODIPY), boron dipyrromethenes (BODIPY) and metal phthalocyanine complexes. Sensor membrane (3) according to one of the Claims 1 to 7 , wherein the optically detectable substance (27) is a high conversion material (photon upconversion material), in particular in the form of nanoparticles (UCNPs). Sensor membrane (3) according to one of the Claims 1 to 7 , wherein the optically detectable substance (27) comprises one or more inorganic luminescent pigments which consist of an inorganic solid which itself shows donor-acceptor luminescence or charge transfer luminescence or is doped with one or more luminescent ions, the or the plurality of luminescent ions is selected or are selected from the group consisting of: In ⁺ , Sn ²⁺ , Pb ²⁺ , Sb ³⁺ , Bi ³⁺ , Ce ³⁺ , Ce ⁴⁺ , Pr ³⁺ , Nd ³⁺ , Sm ²⁺ , Sm ³⁺ , Eu ²⁺ , Eu ³⁺ , Gd ³⁺ , Tb ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ²⁺ , Tm ³⁺ , Yb ²⁺ , Yb ³⁺ , Ti ³⁺ , V ²⁺ , V ³⁺ , V ⁴⁺ , Mn ²⁺ , Mn ³⁺ , Mn ⁴⁺ , Fe ³⁺ , Fe ⁴⁺ , Fe ⁵⁺ , Co ³⁺ , Co ⁴⁺ , Ni ²⁺ , Cu ⁺ , Ru ²⁺ , Ru ³⁺ , Pd ²⁺ , Ag ⁺ , Ir ³⁺ , Pt ²⁺ and Au ⁺ . Sensor membrane (3) according to one of the Claims 1 to 7 , wherein the optically detectable substance (27) comprises an electrochromic material. Sensor membrane (3) according to one of the Claims 1 to 11 The functional layer (23) is covered with a protective, support and / or insulating layer (25) which is permeable to the analyte. Sensor membrane (3) after Claim 12 , wherein the protective, support and / or insulating layer (25) is at least partially embedded in the second polymer matrix covering the functional layer. Sensor membrane (3) according to one of the Claims 12 or 13 , wherein the protective, support and / or insulating layer (25) is formed from a polymer doped with a pigment, in particular a dark pigment such as carbon black or activated carbon. Membrane cap (13) for an optochemical sensor (1, 10), comprising: a sensor membrane (3) according to one of the Claims 1 to 14 and a, in particular cylindrical, housing, the sensor membrane being arranged on an end face of the housing (3). Membrane cap (13) Claim 15 , The housing on its side opposite the end face being designed to be releasably connected to a sensor body (12). Optochemical sensor (1, 10) for determining a measurement variable correlating with a concentration of an analyte in a measuring fluid with a sensor membrane (3) according to one of the Claims 1 to 14 , further comprising: - a probe housing (11) which has at least one immersion area designed for immersion in the measurement fluid, the sensor membrane (3), preferably by means of a membrane cap (13), being arranged in the immersion area of the probe housing (11); - A radiation source (4) arranged in the probe housing (11) for irradiating excitation radiation into the sensor membrane (3); - A radiation receiver (5) arranged in the probe housing (11) for receiving radiation which is emitted by the luminescent dye (24) and / or the optically detectable substance (27); - A in the probe housing (11) arranged sensor circuit (11), which is designed to control the radiation source (4), receive signals from the radiation receiver (5) and to generate and output output signals based on the signals of the radiation receiver (5) . Method for testing and / or identifying a sensor membrane (3) of an optochemical sensor (1, 10) with a functional layer (23) which has a first polymer matrix which is doped with a luminescent dye (24), the emissivity of which after excitation with electromagnetic Radiation can be changed by an analyte, and which has a second polymer matrix in which the functional layer (23) is at least partially encapsulated, and which is permeable to the analyte in at least one partial area facing the measuring fluid and adjacent to the functional layer (23), full: - Using an optical detection method, check whether the sensor membrane (3) contains an optically detectable substance (27) that is different from the luminescent dye (24). Procedure according to Claim 18 , the step of testing comprising: - exciting the optically detectable substance (27) to emit electromagnetic radiation; - Detecting a signal of a radiation receiver (5) which is set up to receive emission radiation from the optically detectable substance (27) contained in the sensor membrane (3) and to convert it into an electrical signal; and - determining on the basis of the detected signal whether the sensor membrane (3) contains the optically detectable substance (27). Procedure according to Claim 19 , In addition, a further test step is carried out, which comprises: - Using a further, in particular optical or chemical, method to check whether the sensor membrane (3) contains the optically detectable substance (27). Procedure according to one of the Claims 18 to 20th , further comprising identifying the optically detectable substance (27). Procedure according to Claim 21 , wherein checking by means of an optical detection method as to whether the sensor membrane (3) contains an optically detectable substance (27) and, if the check shows that the sensor membrane (3) contains an optically detectable substance (27), identifying the optically detectable Substance is carried out by the optochemical sensor (1, 10) by means of a radiation source (4) and a radiation receiver (5) of the sensor and a sensor circuit (11).

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